Communication system



July 9, 1940. H. J. CUNNINGHAM EI AL 2,207,314

COMMUNICATION SYSTEM Filed Nov. 13, 1957 5 Sheets-Sheet 2 FIG. 2

g llll F457 50 GROOME INVENTORS. HANLEV By RICHARDS ATTORNEY y 9, 1940- H. .1. CUNNINGHAM El'AL 2,207,314

COMMUNICATION SYSTEM Filed Nov. 15, 19s? 5 Sheets-Shet 5 2% m? INVENTORS: HAN- By km Ric/1,5525 MM A r TORNEV July 9, 1940. H. J. CUNNINGHAM El AL 2,207,314

- COMMUNICATION SYSTEM Filed Nov. 15, 1931 FIG 4 5 Sheets-Sheet 4 T I I liJ. CUNNINGHAM INVENTORS: DOME EH. HANLEV By K"! RICHARDS A TTORA/E' V July 9, 1940, H. J. CUNNINGHAM ET AL 2,207,314

COMMUNICATION SYSTEM Filed Nov.

13, 1937 5 Sheets-Sheet 5 Patented July 9, 194% pairs PATENT orrrcs COMIVIUNICATION SYSTEM 3., assignors to American Telephone and Telegraph Company, a corporation of New York Application November 13, 1937, Serial No. 174,469

'7 Claims.

This invention relates to communication systems in which a plurality of stations may transmit over the same communication path or channel at substantially the same time by automatically dividing the channel time between the number of stations which are transmitting over it substantially simultaneously, and more particularly to improvements in the telegraph system described in the application of Borgenson et al. Ser. No. 174,468, filed Nov. 13,1937.

An object of this invention is to provide an improved communication system in which the greatest possible channel time is used for transmitting message currents over it.

A further object of this invention is to secure a more even and more equitable division of the channel or line time between the various stations which wish to simultaneously communicate over it.

In accordance with a specific embodiment of this invention a high speed and a low speed startstop distributor are connected to each end of the main line or channel. A plurality of extension lines are operatively connected to the di..- tributors connected to each end of the main line. The high speed distributor is provided to transmit directing impulses over the system for indicating the stations which will transmit in pulses during the next rotation of the low speed distributor. In addition, a circuit arrangement is provided for reversing the connection between the slow speed distributor and two of the extension lines for securing a better time distribution between the extension lines when only a portion of them are active, 1. e., when they wish to transmit impulses. The circuit is also arranged for transferring the connection between the distributors and idle extension lines to active extension lines so that substantially the entire main line time is utilized for transmitting message cur. rents.

The foregoing and other objects of this invention may be more readily understood when the following description of a preferred embodiment is read with reference to the attached drawings in which Figures 1, 2, 3 and 4 show details of a telegraph system embodying the invention;

Fig. 5 shows the manner in which Figs. 1, 2, 3 and 4 are arranged for the complete system; and

Fig. 6 shows in diagrammatic form the elements of the system.

The elements of the system and its general manner of operation will be best understood with reference to Fig. 6. The specific embodiment of (Cl. l78--52). v

the invention as shown is arranged for the simultaneous transmission from three extension stations. It is to be understood, however, that the invention is not limited in any way to three stations which may transmit over a single 0011- ductor but may be employed for any number of extension stations.

As shown in Fig. 6, three transmitting extension stations A, B and C are connected to a transmitting main station I80. This main station is in turn connected to a second main station Hi! to which are connected three receiving extension stations A, B and C. In accordance with this invention station A always transmits to station A, station E always transmits to station B and station C always transmits to station C.

Each of the respective extension stations A, B and C is provided with a tape perforator l82A, i823, and I820, a tape controlled transmitting distributor ESSA, E8313, and i830, and a receiving or recording telegraph device EMA, 18:33, and i840. The respective extension stations are connected over circuits 185A, 353, and 885C to the main station Mt. In general, the connections 185A, 1853, and 5856 between the transmitting stations and the main station H89 include more than a single telegraph channel and in a preferred embodiment of this invention they include more than a single telegraph channel in each direction between these stations.

The main station 589 is provided with groups of relays 286A, "36B, and W5C which are individual to the circuits extending to each of the extension stations. A group of common relays I2? is provided to control the high speed distributor ltd and the low-speed distributor E83. These distributors are driven by motor I96, as shown in diagrammatic form at station Md.

The distributors 588 andlili are in turn connected to line is! which extends to the receiving main station lat. Receiving station it! is provided with a group of common relays which control the slow receiving distributor 92 and the high speed receiving distributor 93. These distributors are connected both to line 59! and to the relay equipments Will, 8943, and ESQ-C individual to the circuits associated with each of the extension stations. The relay circuits lt iA, IIMB, and iQ iC are connected over lines IQBA, WEB, and W5C to the receiving extension stations A, B, and C. These extension stations are provided with receiving teletypewriters 36A, E9613, and W5C or other suitable receiving telegraph apparatus. Lines QQEA, i953, and [95C are not limited to a single one-way cdmmunication channel. However, in general this will be sufficient since it is only necessary to transmit the signal impulses to the receiving stations as they are received from the main line. At the receiving main station I8I the fast and slow distributors are driven by motor I9'I at substantially constant speed and at substantially the same speed as the distributors I88 and I89 at station I80.

A one-way communication system is shown in Fig. 6. It is to be understood, however, that a similar system may be provided for transmission in the opposite direction, in which case both stations A and A, B and B, and C and C will be provided with the same transmitting and receiving apparatus.

Reference will now be made to the system shown in Figs. 1, 2, 3 and 4 when arranged in accordance with Fig. 5.

Fig. 1 shows three subscribers stations A, B and C connected to a central station shown in Figs. 2 and 3. The central station shown in Figs. 2 and 3 is connected by line 58 to a central station shown in Fig. 4, which in turn is connected to three subscribers stations A, B and C.

Line 58 connecting the two central stations may include any suitable telegraph channel including a radio or a carrier current channel. This channel may include suitable repeaters, including regenerative telegraph repeaters, terminal and intermediate composite sets, open-wire lines and cable lines as well as other equipment usually associated with long telegraph or toll lines.

Station A, shown in Fig. 1, is connected to the central station, shown in Figs. 2 and 3, by lines I3, I4, 5 and I6. StationB is similarly connected over lines H3, H4, H5 and H6, while station C is connected over lines 213, 2M, 2I5 and 2I6.

Station A is provided with a telegraph keyboard perforator 59 by means of which the subscriber or operator at station A perforates tape I2 in.

accordance with the information to be transmitted to station A connected to the second central station, shown in Fig. 4. Station A (see Fig. 1) is also provided with a tape transmitter I I which is employed to transmit the signals recorded in tape I2 to the distant station. This tape perforator and transmitter may be of any suitable type and employ any desired code. Examples of apparatus of this type are described in detail in U. S. Patents 1,965,572, Burky et al., July 10, 1934; 1,965,602, Lake, July 10, 1934; 1,969,891, Lake et a1., August 14, 1934; 2,019,505, Reiber, November 5, 1935; and 2,055,567, E. F. Watson, September 29, 1936.

When the operator at station A wishes to transmit messages to station A she will operate keys 9| of the keyboard perforator I9, which in turn cause tape I 2 to be perforated in accordance with the operation of keys 9|. As soon as there is a sufficient supply of perforated tape I2, contacts 92 of the tape transmitter I I will be closed. This completes a circuit for the operation of relay 93 from ground, through the winding of relay 93, the inner break contacts of relay 94, tape control contacts 92 to the positive terminal of rectifier 96. It is assumed that rectifier 96 is energized from source 91 and that the motor and other equipment usually provided for perforators and transmitters is also energized. This additional equipment is not shown or described in detail because it is well known and understood in the art and because it operates in its usual manner. Relay 93 in operating completes a line circuit from ground connected to line I4 at the central station (see Fig. 2), over line I4, through the upper contacts of relay 93, segment I99, brush IBI and segmentI93 of the transmitting distributor, line I3, to the central exchange, and through the upper windings of relays I! and I8, to battery. Current flowing in this circuit causes relays I1 and I9 to move to their left-hand positions. These relays are normally maintained in their right-hand positions by current flowing in an obvious circuit through their lower windings. However, the current flowing through their upper windings in the above described line circuit overpowers the eifect of the current flowing through the lower windings of these relays and causes the relays to move to their left-hand positions. he lay I! in operating to its left-hand position completes a circuit from negative battery through its armature and left-hand contacts, winding of relay 38, left-hand contacts of relay 39, segment BI of the fast transmitting distributor I39, brush 89 and segment I40 to ground.

Relay 38 in operating completes an obvious circuit for the operation of the start magnet 49 of the fast distributor I39. Start magnet 45 in operating releases the brush arm 33 for rotation.

Brush arm 83 is driven through a friction clutch, not shown in detail, from shaft 19, which is in turn driven through gears I5 by motor I4. Motor 74 is connected to a source of power which causes it to operate continuously at a substantially constant speed. Details of the motor control circuit, as well as the friction clutches have not been shown or described in detail because they are well known and operate in the usual manner.

Brush arm 83 in rotating carries brushes B4 and 89. During the time brush 84 is passing over segment I4I, a circuit is completed for the operation of relays 39 and. 48 from ground, through the upper winding of relay 48, segment 53 of the fast distributor I39, brush 34, segment I4I, to

positive battery through the left-hand winding of relay 39.

Relay 39 in operating interrupts the operating circuit of relay 38 through its left-hand contacts and completes a locking circuit from positive battery, through its right-hand contacts and winding of relay 39, to ground, through the left-hand contacts of relay 45.

Relay 48 is normally held in its right-hand position by current flowing through its lower winding. However, the current flowing through its upper winding through the above-described circuit overcomes the effect of the current flowing through the lower winding and causes its armature to move to its left-hand position. operating to its left-hand position interrupts the circuit of line 58 which causes relays 49 and 59 at the second central exchange station, shown in Fig. 4, to also move to their left-hand positions due to current flowing through their upper windings. Relay 59 in operating to its left-hand position completes a circuit for the operation of the start magnet 52 of the fast receiving distributor I42, from battery, through the left-hand contact and armature of relay 50, segment I43 of distributor I42, brush I44, segment I45, through the winding of the start magnet 52 to battery through the left-hand contact of relay 53.

Start magnet 52 in operating releases brush arm I46 which starts to rotate with shaft BI through a friction clutch, not shown. Shaft 82 is rotated through gears 82 by motor I8. Motor I9 continuously operates and rotates shaft ill at substantially the same speed that motor 14 ro- Relay 48 in 'i tates shaft I6. The governors or other speed 0011- 75 trol apparatus of these motors are of the type usually employed for start-stop telegraph systems. Shafts l6 and 8| need not be rotated in exact synchronism, it being suflicient if they are rotated at substantially the same speed. It is usually desirable to cause shaft 8! to rotate slightly faster than shaft 16 so that the two brush arms M and 83 will always start to rotate substantially together. In addition, the start relay 38 is made slow in operating to allow sumcient time to insure that the receiving distributor brush arm has time to complete its revolution before the transmitting distributor starts on the next revolution. These synchronizing arrangements are well known and are employed in the usual start-stop telegraph systems so they need not be described in greater detail here.

During the time brush IN is passing over segment Ml a circuit is completed for the operation of relay 53 from positive battery, through the left-hand contact and armature of relay 50, segment MS of fast distributor I42, brush I44, segment Nil, the left-hand winding of relay 53 to negative battery through the right-hand contacts of relay 5i. Relay 53 in operating interrupts the operating circuit of the start magnet 52 and completes a locking circuit from ground, through its right-hand contacts and right-hand winding, to battery through the right-hand break contacts of relay 54.

Brush arms 83 and 1% now continue to rotate substantially in synchronism and complete one revolution. During the time brush 84 of the fast transmitting distributor is passing over :the center portion of segment 33, brush M4 of the fast receiving distributor M2 passes over segment 3?. During this time a circuit for the operation of relays 23 and A8 in series may be traced from positive battery, through the armature and lefthand contacts of relay l8, winding of relay 23, segment 33, brush 8 and segment 59 of the fast transmitting distributor, tov ground through the upper winding of relay 4%.

Relay 23 in operating completes a circuit for the operation of relays 2d and 25 in series from battery through the right-hand break contacts of relay t5, the contacts of relay 23, to ground through the windings of relays 24 and Z5.

Relay 2Q in operating completes a locking circuit for holding relays 2d and 25 operated from battery, through the right-hand break contacts ofrelay 45, left-hand contacts of relay 2%, to ground through the windings of relays 24 and 25. Relay 2 in operating also completes a transmission circuit from the left-hand contacts of relay it, the right-hand armature and make contacts of relay 2 3, tosegment 34 of the slow trans mitting distributor.

RelayZE in operating completes a transmission path from the right-hand contacts of relay H, the innermost left-hand make contacts of relay 25, over line iii, lower contacts of relay 93 toground through the winding of the receiving relay 25 of the recording teletypewriter equipment at station A. Relay 25 in operating also completes a circuit from ground, through the winding of relay 9d at station A, line 55 and lefthand outer make contacts of relay 25, tosegment 35 of the slow transmitting distributor.

The above described circuit for operating relays 23 and 38 in series causes relay 18 to remain in its left-hand position during the time brush 8% passes over segment 33 of the fast transmitting distributor. Consequently, relay 59 will be maintained in its leftehand position by current flowing through its upper winding in an obvious circuit during the time brush M4 of the fast receiving distributor I42 is passing over segment 3i. During this time a circuit is completed for the operation of relay 26 from ground, through the winding of relay 26, segment 3i, brush I48 and segment I43 of the fast receiving distributor to positive battery through the armature and left-hand contacts of relay 5%. Relay 26 in operating completes a locking circuit from battery through the left-hand break contacts of relay E i and the right-hand make contacts of relay 26, to ground through the winding of relay 26. Relay 2% in operating also completes a circuit from segment 36 of the slow receiving distributor M8 to line l'H.

- If the subscribers at stations B and C wish to transmit messages at substantially the same time they will also operate their keyboard perforators H8 and 210, respectively, and cause the operation of the corresponding relays associated with the lines connected to these stations through the remainder of the revolution of brush arms 83 and M 5. First, it is assumed that each of the stations A, B and C wish to transmit at the same time, i. e., all the lines are active.

Just before brush arm 83 comes to rest, it I completes a circuit for the operation of start magnet 4! of the slow transmitting distributor receiving distributor M8, from battery, through the winding of start magnet 5i, segment Hi9, brush Mdand segment I43 of the fast receiving distributor, to battery through the armature and left-hand contacts of receiving relay 5 3.

During W the time brush arm 144 is passing over segment M9, receiving relay 50 is maintained in its lefthand position by relay &8, which in turn is maintained in its left-hand position in a circuit from battery through segment I59 of the fast transmitting distributor, brush B4 and segment 59, to ground through the upper winding of relay 48.

It should be noted that the line time required to transmit the directing impulses as described above is independent of any limitations of speed, segment length, etc., of the slow distributors. Instead, it is limited only by the line and associated high-speed distributors and thus it requires a minimum of line time to transmit the directing impulses so the maximum line time is l available for the transmission of message currents.

The brush arms 8% of the slow transmitting distributor and |5I of the slow receiving distributor are rotated through friction clutches by shafts 69 and M3, respectively. Shaft is rotated by motor I l through gears '55, shaft it and gears H, while shaft Bil is rotated by motor 18 through gears 82, shaft 3i and gears "Iii. Shafts 69 and 80 are rotated at substantially the same speed just as shafts l6 and 8| are. When these brush arms 86 and l5l are released they rotate substantially together through 360 degrees. During the time brush 8i is passing over segment 35 of the slow transmitting distributor, brush E52 passes over segment 36 of the slow-receiving distributor, and so on.

During the time brush 88 of the slow transmitting distributor passes over segment 35, it

connects positive battery thereto and causes the operation of relay 94 at the 'subscribers station A in the circuit over lead I 5, pointed out above. The operation of relay 94 completes a holding circuit for holding relay 93 operated from ground, through the winding of relay 93 and uppermost make contact of relay 94 to the positive terminal of rectifier 95. Relay 93 is slow in releasing so that it will remain operated during any short time interval between opening of the contacts of relay 94 in its (relay 93) operating circuit and the closing of the contacts of relay 94 in the holding circuit of relay 9S. Relay 94 in operating also causes the operation of the start magnet 98 in a circuit from the positive terminal of rectifier 98, through the tape control contacts 92 and upper inner make contact of relay 94, to ground through the winding of start magnet 98.

The operation of start magnet 98 withdraws stop latch 99 and releases the brush arm IUD. When brush arm I90 is released it is driven through a friction clutch, not shown, and causes brush IUI to successively connect segments I38, I04, I05, I95, I91, I99 and I89 to line I3. This causes the transmitting distributor at the sub scribers station to transmit telegraph signal impulses in accordance with the perforations in tape I2. The contacts I92 connected to these segments are controlled by the perforations in tape I2 so that these contacts are connected to line I4 through the contact of relay 93 when there is a perforation in tape I2 under or over the respective contacts.

After brush arm I05 has made one revolution, apparatus not shown but well understood in the art, causes tape I2 to be advanced one position and the above operation repeated to transmit the next signal impulse. At the central station relays I1 and I8 are operated in accordance with the telegraph signal impulses transmitted from station A. The impulses are repeated by relay I! through the inner left-hand make contacts of relay 25 to the receiving relay 95 at the subscribers station, which in turn repeats the impulses to the printer magnet I53 at the subscribers station to record the transmitted signals for a home copy. It should be noted that relay 95 is normally maintained in its left-hand position by current flowing in an obvious circuit through its lower winding and is operated to its right-hand position by current flowing through its upper winding over line I6. It should also be noted that relay Il reverses the signal impulse, that is, the circuit from the right-hand contact of relay I! is completed or closed during the time the circuit through its upper winding and line I3 is open or interrupted and vice versa. However, since relay 95 interrupts the circuit of the printer magnet I53 when the circuit of line I6 is completed, relay 95 again reverses the signal impulses so that the circuit of magnet I53 is closed during the time line i3 is closed and is opened during the time the line I9 is opened. Thus magnet 853 receives substantially the same signals as transmitted over line I3.

Relay I8 also follows the signals transmitted over line I3 and repeats them to relay 48 in a circuit from the contacts of relay I8, the righthand make contacts of relay 24, segment 34, brush 8'! and segment 62 of the slow transmitting distributor through the upper winding of relay 48. Relay 48 in turn repeats the signal impulses to relays 49 and 59 at the second central station over line 58. Relay 49 in following these signal impulses repeats them to the line relay 2! at the subscribers station A over a circuit from the contacts of relay 49, segment I54, brush I52 and segment 35 of the slow receiving distributor, left-hand armature and make contact of relay 26 over line I'I'I to the upper winding of receiving relay 2'! at the subscribers station A.

Here again relay 48 causes the signal impulses to be inverted, that is, current flows in line 58 during the time no current flows in line I3, while no current flows in line 58 during the time current flows in line I3. Relay 49 repeats the inverted signal impulses to relay 2'! at the subscribers station A. However, relay 2'! at the subscribers station A again inverts the signal impulses so that the current flowing through the receiving printer magnet 28 corresponds to the transmitted current flowing in line I3 and thus the receiving printer equipment at station A receives the same signals as transmitted from station A and correctly responds thereto.

When brush 88 passes off segment 35 it interrupts the circuit of relay 94 and permits this relay to release. Relay 94 in releasing permits the stop magnet 98 of the transmitting apparatus II to release, which in turn releases latch 99 and causes the brush arm IIIO to come to rest after the completion of the revolution then in progress. This interrupts the transmission from station A. It should be noted that the segment 34 should be somewhat longer than the segment 35 since the transmission from station A is not interrupted at once when brush 88 passes off segment 35 but continues until brush arm I 90 comes to rest against the stop latch 99. During this short interval of time it is necessary that the transmission path from station A be completed through the slow transmitting distributor as well. as the slow receiving distributor at the second station to the subscribers station A. It is also desirable to have relay 93 slow in releasing so as to insure maintaining line I4 closed until brush arm comes to rest if both contacts 92 and relay 94 release at about the same time. This insures the proper transmission of the last code combination.

If during the time interval that the transmission path is completed from station A to station A the supply of perforated tape I2 becomes exhausted, the tape stop contacts 92 will be opened. This interrupts the circuit of the start magnet 98 which releasesstop latch 99 and causes brush I00 to come to rest at the completion of the revolution then in progress. Then when relay 94 releases at the end of the interval of time during which the transmission path is completed between stations A and A, the circuit at station A will return to its normal condition.

During the succeeding intervals of time during which brush 81 is passing over segments I 34 and 234 similar transmission circuits are com- .pleted from station B to station B and from station 0 to station C, during which times the apparatus at these stations transmits the signal impulses to corresponding stations B and C in the same manner as described above for station A.

At the end of the first revolution, just before brush arm 86 comes to rest, a circuit is completed for the operation of relay 45 from negative battery through its winding, segment 255 of the slow distributor, brush 8?, segments 256 and 63 of the slow distributor to positive battery. Relay 45 in operating interrupts the locking circuit of relay 39 and permits this relay to release.

Relay 3%! in releasing connects the winding of relay 38 to segment ii and permits relay 3% to again be operated ii any of the subscribers at stations A, B or C still have additional information to be transmitted to the corresponding stations A, B and C", whereupon the above-de scribed cycle will be repeated.

The operation of relay {i5 also interrupts the locking circuits for relays 2t, 25, 12d, E25, 2W4

and 225 and permits these relays to release so that they may be again reoperated under control of the fast distributor during its next revolution. Relay 15 in operating also completes an obvious circuit for the operation of relay 43. Relay 43 in operating completes a circuit for the operation of relays 55], ll and it from ground, through the windings of relays 32, 5! and til, the righthand contacts of relay d3, the right-hand break contacts of relay 44 to battery. The operation of relays it, ll and t2 reverses the transmission and control circuits between stations B and C, as described below. The operation of relay 3% completes a locking circuit for relays ill, 45 and 22 from ground, through their windings, the innermost lower make contacts of relay id, to battery.

When brush 8% passes off segments 255 and it interrupts the circuit of relay 45 and permits this relay to release. Relay 4%: in releasing prepares the locking circuits for relays 29, 2d, Mid, H25, 224 and 225 so that these relays may again be locked operated under control of the various subscribers stations and distributors. Relay 15 in releasing also interrupts the operating circuit of relay G3, which in turn releases. In releasing relay d3 completes an operating circuit for relay 44 from ground through the wind ing of relay :4, the left-hand break contacts of relay 43, the lower make contacts of relay til, to battery. Near the end of the next revolution of the slow transmitting distributor relay 45 vis again operated and again interrupts the locking circuits of relays till, 24, 25, are, E25, 22d 225, as described above. The second operation of relay again completes the operating circuit for relay 3. The operation of relay d3 at this time, however, short-circuits the windings of relays lll, l-i and 42 by connecting ground from the right-hand make contacts of relaysdd and 63 to the right-hand winding terminal of relay ll. This causes relays Mi, ll and 42 to release and restore the control and transmission circuits from stations B and C to their original condition. When relay 55 again releases after brush 3? passes off segments 255 and 256, it in turn causes relay 43 to release. Relay 43 in releasing short-circuits the winding of relay M by connecting ground fom the lower break contact of relay i l, through the left hand contact of relay to the upper winding terminal of relay M. This causes relay M to release, at which time the relays in the associated circuits at the first central station are inthe same positions they originally were at the beginning of the first revolution of the slow distributor. During the succeeding revolutions of the slow distributor the above cycle of operation of relays t5, i l, 53.; d2, :ii and so is repeated, which reverses the control and transmission circuits between stations B and C during alternate revolutions of the slow I transmitting distributor.

At the second central station the operation of I revolution of theslow receiving distributor relay 54 is operated, which in turninterrupts the locking or holding circuits of relays 53, 2t, 1525 and 226 and permits these relays to return to their normal positions. Relay 54 in operating also completes the operating circuit for relay 56,

which in turn causes the operation of relay 5?. When relay 5t releases, just before brush l52 comes to rest, it releases relay 56, which in turn completes the operating circuit for relay 515. The

operation of relay5l reverses the transmission circuits to stations 3' and C. Near the end of second revolution of the slow receiving distributor M8. relay 54 is again operated and operates relay 55. The operation of relay 5E short-circuits the winding of relay 5! by connecting ground to its left-hand terminal. Relay .5? releases and restores the transmission circuits to stations B and C to their original condition. When relay 54 again releases it in turn releases relay 5t Release of relay lit at this time connects ground to the upper winding terminal of relay 55, causing relay 55 to release. Thus at the end of the second revolution these relays at the second central station are again returned to the same condition they were at the beginning of the first revolution.

During the first revolution of the slow dis-- tributors the transmission and control paths from station E to station B may be traced" through relays H1, H8, leads H29, H5. and

M6, the normal or break contacts of relaysdfl,

During the next revolution of the slow distributors relays Mi, 4!, Q2 and 5'! will be operated and interchange the transmission and control paths between stations B and C so that during the second revolution of these distributors the transmission and control paths from station B may betraced as follows: From station 3 over lines H3, H4, H5 and l l6, through relays ill, M5, the operated contacts of relays 4B; 5;! and 52, over leads 2E8, 229, 225 and 222, through. relays E23,

220; and 225, slow transmitting distributor segments 23 and 235, slow receiving distributor segments led and 236, relay22 and operated contacts of relay 5'! to station 33; Similar transmission and control circuits may be traced from station' C through the slow distributor segments ls l, I35, and operated contacts of relays at, 4! and 42 to station C through the slowreceiving distributor segment I36 and operated contacts of relays E26 and 5l.- I

Thus during the first revolution of the slow transmitting distributors the first transmission interval is assigned to station A, the second interval to station E and the third interval to station C, while during the second revolution the first transmission interval is again assigned to station A, the second transmission interval is now assigned to station C and the'third transmission interval to station B. During the third revolution and each odd succeeding revolution, time intervals are assigned as during the first revolution of 5 the slow distributors. During the even-numbered revolutions time intervals are assigned to stations A, B and C as described during the second revolution of the slow distributors.

It is essential that the position of relay 5? at the second central station correspond to the position of relays 40, 4| and 42 at the first central station so that the transmission circuit from station B will always be connected to the transmission circuit to station B and the transmission circuit from station C will always be connected to the transmission circuit to station C.

The object of alternately reversing the transmission path from stations B and C to stations B and C during alternate revolutions of the slow distributors is to evenly divide the time assigned to any two of the stations if only two of the subscribers thereat wish to transmit messages simultaneously, 1. e., one of the extension lines to the subscribers stations is idle and the other two are active. In the foregoing description it was assumed that each of the subscribers at stations A, B and C wished to simultaneously transmit to the corresponding stations A, B and C. However, if the subscribers at only two of the stations wish to simultaneously transmit to their associated stations, two intervals of time will be assigned to one of the stations and one interval of time to the other station during the first revolution of the slow distributors. During the second revolution of the slow distributors only one interval of time will be assigned to the firststation and two intervals of line time will be assigned to the second station.

Assume, for example, that the subscribers at stations, A and B wish to simultaneously transmit messages to the corresponding stations A and B but that the subscriber at station C does not wish to transmitinformation to station 0'.

During the first revolution the fast distributors at both the first and second central stations, relays 24, 25, I24 and I25 at the first station will be operated and relays 26 and I26 at the second central station will be operated. During the first interval of line time during which brushes 3'! and 88 are passing over segments 34 and 35 of the slow distributor the transmission and control circuits are completed from station A through these segments 34 and 35 to line 58. At the second central station the transmission circuit is completed from the receiving relay 49 connected to line 58 through segment 36 and relay 26 to station A over line 9.

During the second interval of line time the control and transmission circuits from station B are completed through segments I34 and I35 to line 58 and thence through segment I36, relay I26 and the break contacts of relay 5! to station B.

During the third interval of time during the first revolution of the slow distributor when brushes 8'! and 88 are passing over segments 234 and 235 the transmission and control circuits are completed from station B through the make contacts of relays I24 and I25 and the break contacts of relays 224 and 225, to segments 234 and 235 of the slow transmitting distributor to line 58. At the second central station the transmission path is extended from the contacts of relay 49 through the segment 236 of the slow receiving 1 distributor, the normal contacts of relay 226, the operated contacts of relay I26, the normal contacts of relay 51 to station B over line I'IZ.

Thus during the first interval of time during the first rotation of the slow distributors the transmission path is completed between station A and station A. During the second and third intervals of time the transmission path is completed between station B and station B.

During the first interval of time during the second revolution the transmission path from station A will again be completed to station A over the same circuits described during the first interval of time during the first revolution of the slow distributors. During the second interval of time of the second revolution of the slow dis tributors, however, the transmission path from station A to station A is completed. As pointed out above, during the second revolution of the slow distributors relays 40, 4| and 42 at the first central station and relay 5'! at the second central station are operated. This means that during the second revolution of the fast distributors at these stations relays 24, 25, 224 and 225 at the first station and relay 23 and 228 at the second central station are operated. Thus during the second interval of time during the second revolution of the slow distributor the control and transmission circuits may be traced from station A through the operated contacts of relays 24 and 25 and the normal or break contacts of relays I24 and I25 through segments I34 and I35 of the slow transmitting distributor to line 58. At the second central station the transmission circuit extends from the receiving relay 49, through segment I36 of the slow distributor I48, the normal or break contacts of relay I26 and the operated or make contacts of relay 26 to station A over line I'II.

During the third interval of time of the second revolution of the slow distributors the transmission path from station B may be traced through the make contacts of relays 224, 225 and segments 234 and 235 of the slow transmitting distributor to line 58. At the second central station receiving relay 49 repeats the received signal impulses to station B over a circuit through segment 236 of the slow receiving distributor I48, the operated contacts of relay 226 and the operated contacts of relay 5! over line I12.

Thus during two revolutions of the slow distributors the line time 'is equally assigned be tween stations A and B. Similar circuits may be traced for transmission between any of the other two sets of stations whereby the line time is always equally divided or assigned to the two stations at which the subscribers Wish to simultaneously transmit signal impulses to their associated stations.

If only one of the subscribers wishes to transmit from his station to the associated station substantially the entire line time is assigned to the station at which the subscriber wishes to transmit. Assume, for example, that the subscriber at station A is the only subscriber wishing to transmit messages to station A at a given time. Under theseconditions only relays 24 and 25 at the first central station and relay 26 at the second central station will be operated during the rotation of the fast'distributors. 7

During the first interval of time of the first revolution-of the slow distributors transmission circuit from station A to line 58 is the same as described above when two or three subscribers all wish to transmit simultaneously. During the second interval of time the control and transmission circuits from station A may be traced from station A, through the make contacts of relays 24 and 25 through the break contacts of relays I24 and I25, the segments I34 and I35, to line 58. At the second'central station the transmission circuit extends from the receiving relay 49, to

During the third interval of time'dur ing the first revolution of theslow'distributors line Hi;

the transmission and control circuits extend from station A to line 553 throughthe make contacts'of relays 2t and-2t;breal: contacts, of relays l'id'and 625 and the break contacts of relays ti -land 225, through segments 2% and 235. At the" second central station the transmission path extends from the receiving relay 4-3, through segment of the slow receiving distributor M8, through'the left-hand break contacts of relay 2253, the left hand break contacts of. relay H26 and the lefthand make contacts of'relay 28 to stationA' over line ill. During the second revolution of the slow distributor the time intervals are again all assigned to station A over the similar circuits scribed above during he first revoluti except that the connectionsbetween the last two sets of distributor segments it l, itb and i3il'and 23 i;

and 23% are reversed. 7

Similar circuits are provided whereby substantially the entire line timemay be assigned to station B if the subscriber. atfstation B is the only subscriber wishing to transmit at a given time. Other similar circuits are also provided whereby the line time is substantially all assigned to station C if the subscriber thereat is the only subscriber desiring to transmit at a given time.

As pointed out above, when all three subscribers are transmitting certain time must be allowed between transmissions by the various subscribers to insure that the transmission circuit has been switched from one to the other. Inasmuch as the distributors at both stations are'not run at exact synchronism this interval of time must also include sufiicient time to allow for the difference in speed of the distributors at both ends of the line. In order toprovide for this time interval the segments iSE and 235 are separated from each other by short segments lid, 65 and the control segment 25?. If all the subscribers wish to simultaneously transmit the circuits of short segments E i and 65 are interrupted by relays 25, 525 and 225. The time interval during which brush arm 86 carrying brush 88 passes over thesesegments is suficient to insure proper switching of the transmission path from each station to the succeeding station.

If, however, the transmission during any two succeeding time intervals is to be to the same station this time interval is not required because 'it.

is not necessary to switch the transmission path from one station to the next. Assume, for ex ample, as described above when subscribers at only stations A and B wish to transmit to their associated stations at a given time. During the second and third intervals of time of the first revoiution of the slow distributor the line is assigned to station E. Thus between these two intervals of time it is not necessary to perform any switching functions. Consequently, under this condition the circuit of segment 65 is completed to segment H35 through the outer right-hand break contacts of relay 222'. Similarly, during the first and second intervals of time during the second revolution the line time is assigned to station A. Consequently, it is not necessary to perform any switching between these time intervals. Under these conditions, segment be is connected to segment 35 through the inner right-hand break contacts of relay 525.

Similarly, if the subscriber at only one station is transmitting at a given time it is unnecessary to perform any switching functions between the various time intervalsso that segments M and 65 are "connected over circuits similar to those des'crib'ed above to segments 35 and H5. Brushes 8i and i52 should be of a bridging type so that thc'e' -willmake contact with the next succeeding segment'beiore they break-contact with the segment over; which they,are passing. This will insure that the transmission path between the various stations is not interrupted or interfered with when brush ill or 2'52 passes on one segmentto another in case the transmission is from the same station during the time the brushes are passing over both of the segments.

In this manner the line time usually employedforiswitching may be employed for transmitting the signal impulses between the transmitting and associated receiving stations.

What is claimed is:-

i. A communication system comprising a main line, extension lines, means for establishing an operative connection between each of said extension lines and said main line comprising a slow speed start-stop distributor connected to.

said'main line, means for extending all of said operative connections to only active extension lines, and additional distributor means for transmitting directing impulses over said main line to indicate the active extension lines.

2. A telegraph system comprising a main line, a start-stop distributor connected thereto, a plurality of extension lines, means for establishing an operative connection between each of said extension lines and said distributor, and means for alternating the connections between two of said connections and said distributor.

3. A communication system comprising a main line, a plurality of extension lines, a start-stop distributor connected to said main line, means for establishing an operative connection between each of said extension lines and said distributor, switching means included in said operative connection for extending all of said connections to only active extension lines, and

means for securing a more eificient distribution of main line time between said operative connections, comprising a second high speed start stop distributor also included in said operative connection, and reversing relays connected in said connection for alternately reversing the connection between two of said operative connections. v

4. A telegraph system comprising a main line, a high speed start-stop distributor connected to each end of said line, a low speed start-stop distributor also connected to each end of said line, an operative connection between said distributors for starting said slow distributor during each revolution of said high speed distributor, a plurality of extension lines, an operative comprising a slow speed start-stop distributor connected to said main line and each of said extension lines for providing a communication path between each of said extension lines and said main line during a portion of each revolution thereof, apparatus connected to said distributor for extending all of said paths to only active extension lines, a high speed start-stop distributor connected to said main line for transmitting impulses thereover indicating the active ex- I tension lines.

6. In a telegraph system, a main line, a plurality of extension lines, operative connections between each of said lines and said main line comprising a start-stop distributor connected to said main line and to each of said extension lines for completing a communication path between said extension lines and said main line during a portion of each revolution thereof, and instrumentalities connected between two of said extension lines and said distributor for reversing the connections between said lines and said distributor during alternate revolutions of said distributor.

7. In a telegraph system, a main line, a number of extension lines cooperating with one end of said main line, the same number of extension lines cooperating with the other end of said main line, means for establishing an operative connection between each of said extension lines and respective ends of the main line comprising a slow speed start-stop distributor connected to said main line and to each of said extension lines, apparatus connected to two of said operative connections for interchanging the connection between said operative connections and said main line during alternate revolutions of said distributor, additional apparatus for extending all of said operative connections to active extension lines, a high speed distributor connected to each end of said line controlled by said extension lines, a control circuit connected to said high speed distributors for transmitting over said main line control impulses which indicate the extension lines which will be active during succeeding revolution of the slow speed distributor,

and means for starting said slow speed distributor during each revolution of said high speed distributor.

HAROLD J. CUNNINGHAM. PRESTON E. GROOME. FRANK H. HANLEY. KENNETH W. RICHARDS. 

